Mesh artifacts only on render
You have a big and ugly n-gon (a polygon of more than 4 vertices) trying to bend as that curve.


You need to subdivide it into more faces.
Here's what you get when you delete that n-gon and do grid fill:



The curvature is better but far from ideal (plus you get terrible topology).

Try to create a curve that has the same number of vertices for both sides (and try to keep the rest of the topology as quads)